More than 60,000 young adults (YAs) aged 18-39 are diagnosed with cancer in the US each year. Advances in treatment have yielded five year survival rates >70% suggesting that the majority of YAs will become long-term cancer survivors. Symptom (e.g., pain, fatigue, distress) interference is common for YA cancer survivors and impacts their abilities to achieve normative life goals (e.g., returning to work/school, achieving autonomy, pursuing social/romantic relationships) and adhere to recommended follow-up care. Symptom management has been identified as a significant issue in the transition to survivorship for YAs by the Institute of Medicine and National Cancer Institute, and assistance with symptom management is rated as an important and unmet need by YA survivors. Yet, behavioral symptom management interventions have not targeted the needs of those diagnosed as YAs. The proposed study aims to develop and test the feasibility and acceptability of a novel behavioral symptom management intervention designed for survivors of YA cancer (cancer types: hematologic, breast, or gastrointestinal cancers, melanoma, or germ cell tumors). The hybrid intervention will include in- person, group sessions and an integrated mobile application. The intervention will provide peer support while also teaching skills to improve symptoms, symptom interference, and self-efficacy for symptom management. The mobile application will assist with symptom monitoring, home skills practice, and connecting with group members. The preliminary version of the intervention will be guided by the research team?s prior work developing and testing symptom management interventions for cancer survivors, national guidelines for YA oncology, consultation with an expert advisory board, and input from patient (3 groups, n=10/group) and provider (1 group, N=10) stakeholders obtained during focus groups. The intervention will be further refined following review by patient user testers (n=10). Next, feasibility, acceptability, and distributions of change over time as well as relationships between outcome variables will be examined through a pilot randomized clinical trial of the developed intervention. Participants (N=60) will be randomized to intervention or wait-list control arms. Primary study outcomes are symptom (pain, fatigue, distress) severity and symptom interference. Self-efficacy and support will also be examined as mediators of change in outcome variables. The proposed study has the potential to make several significant contributions by targeting an underserved group of cancer survivors, addressing a critical gap in care, and addressing variables consistently linked to social, economic, and health burden for YAs. It will also provide important information about approaches to identify, recruit, and retain YA cancer survivors in research and provide pilot data for a larger trial. Formal training in the following areas will strengthen the PI?s ability to become an independent investigator developing, evaluating, and disseminating interventions for YA cancer survivors: 1) clinical trial design and statistical methods, 2) use of mHealth technology for research and intervention delivery, 3) needs of cancer survivors diagnosed as YAs, and 4) professional development.